This application relates to torque applying and measuring apparatus and, in particular, to electronic torque wrenches. The application relates specifically to indexable torque wrenches.
Typically, torque wrenches, such as electronic torque wrenches, provide an elongated lever arm with a coupling mechanism, such as a drive lug, on a coupling head fixed at an end of the lever arm and disposed for coupling to an associated socket tool, fastener or other device to be torqued. In a typical arrangement, the coupling device includes a drive lug projecting from the lever arm substantially perpendicular thereto. U.S. Pat. No. 4,643,030 discloses such an arrangement, wherein the torque sensing means comprises a strain gauge assembly disposed on the coupling head and connected by suitable electrical connections to display apparatus carried by the lever arm. In many cases, in using such a fixed-head wrench, a universal joint or the like is required between the head and the fastener in order to reach the fastener. This decreases the accuracy of the measurement.
It is also known to provide indexable torque wrenches, wherein the coupling head is indexable or pivotally movable relative to the lever arm to facilitate access to fasteners in certain applications, such a wrench being disclosed, for example, in U.S. Pat. No. 4,958,541. In such wrenches the torque sensing means, such as a strain gauge assembly, is located on the lever arm.
This application discloses improved torque wrenching techniques which avoid disadvantages of prior techniques while affording additional structural and operating advantages.
An aspect of the disclosed technique is the provision of an indexable-head torque wrench which affords accurate torque measurement.
In connection with the foregoing aspect another aspect is provision of an indexable-head torque wrench wherein the accuracy of the torque measurement is enhanced.